Body Composition

Body composition is the difference between the amount of lean body weight compared to fat weight. Body fat composition is usually expressed as a percentage of fat. The recommendation for men is 12-16% and women 20-25% body fat. Lean body weight includes all muscles, bones, skin, hair, blood, basically everything except fat weight.

Body composition is an essential measure of health and fitness for both athletes and the general population.
If you are considering a weight loss program, accurately assessing your body fat percentage is the most important measurement you can take.

Even if you wanted to gain weight simply measuring your body weight is not enough. Some athletes would fall into the obese category of height/weight tables despite having very little body fat.

It would be easy to slip into all the negative consequences of excess body fat. Stay on the positive side when calculating body fat percentage. It is important to general health.
Studies are showing that a person living in the western world loses muscle and gains fat starting at age 20.

Even if a person maintains a steady weight throughout their life there's a good chance their body fat percentage is increasing and their lean tissue mass is decreasing.

Storage Fat -- This consists mainly of fat deposited just under the skin. Storage fat for men and women is similar. For the average man 12% of bodyweight is storage fat and for the average woman 15% of bodyweight is storage fat.


Essential Body Fat -- For the body to function normally and healthily a certain amount of body fat is required. This is called essential fat. For women the average amount of essential fat is 12% of bodyweight and for men it is 3%.
 

Trying to achieve a body fat percentage that is so low it affects your essential fat stores is NOT good for your health. Some storage fat is also required for good health because it is important to protect the internal organs in the chest and abdomen.

Ways to calculate

Accuracy, Reliability, Cost and  Availability. They are all important factors to think about when deciding which ways to calculate your body composition.

Body Mass Index (BMI)
BMI is a very simple tool. It's best use is for risk assessment for the general population.

BMI = Body mass in kilograms ÷ (Height x Height in meters) (Divide weight in lbs by 2.2046 to get weight in kg's)

So as an example a 150lb (68kg) woman who is 165cm (1.65m) tall...


BMI = 68 ÷ (1.65 x 1.65)
= 68 ÷ 2.7
= 25


This person has a Body Mass Index of 25.

Well there is a link between BMI and many major degenerative diseases. As a person's BMI increases so does their risk of ill health.


Body Mass Index Classifications
Classification Risk BMI Score
Underweight Moderate less than 18.5
Normal Very low 18.5 - 24.9
Overweight Low 25.0 - 29.9
Obese Class 1 Moderate 30.0 - 34.9
Obese class 2 High 35.0 - 39.9
Extreme obesity Very high greater than 40.0



BMI will be inaccurate for many athletes. BMI doesn't calculate body fat so it can't make allowances for muscular development. Athletes such as bodybuilders, football players, throwing athletes and anyone on a weight training program should avoid using BMI as a way to calculate body fat. Growing children and very elderly adults should also avoid using BMI as a way to calculate body fat.
 

Skinfold Measurements

The most reliable technique used to calculate body fat percentage. Body fat calipers are just about the most cost effective way to calculate body fat.

This method is the most widely used body composition testing method for assessing percent body fat. Equipment used for this assessment includes a skinfold caliper. A Skinfold Caliper is designed specifically for simple accurate measurement of subcutaneous tissue. Either a 7 or 3 site skinfold may be assessed.

7 site skinfold:
chest
triceps
subscapular
axilla
suprailiac
abdomen
thigh

3 site skinfold (Men):
chest
abdomen
thigh

3 Site Skinfold (Women)
tricep
suprailiac
thigh

How accurate is it?
If each test is performed correctly according to the recommended guidelines, there is a +/- 3% error. Validity (compared to underwater weighing): 7 site skinfold (r = .90), 3 site skinfold (r = .89).*


Advantages

 Unlike Height-Weight tables and BMI they actually calculate body fat percentage.
They can be used to calculate body fat in the privacy of your own home.
They are portable. You can test others in the most convenient place for them.
 Used correctly they are an accurate and reliable way to calculate body fat.
It can be a quick way to calculate body fat percentages for a large number of people in a short space of time.
 

Disadvantages

For accurate results an experienced examiner is needed. It really is hard to find the precise locations.
There are different equations used for different people to calculate body fat percentage from skinfolds. Choosing the wrong equation has a big effect.
It is very difficult to test yourself. You may have to ask a friend or family member and this can make skinfold testing unreliable.
Really cheap calipers won't stay very accurate for long. They aren't as accurate as the more expensive.

Bioelectrical Impedence

 Standing barefoot on metal foot plates, an undetectably low voltage electric current is sent up one leg and down the other. Since fat is a very poor conductor of electricity, a lot of fat will impede the current more so than a lot of lean tissue. By measuring the resistance to the current, the machine estimates the percent body fat.

How accurate is it? BIA accuracy, if done correctly on properly operating equipment, is approximately +/- 3%. However, accuracy is dependant upon several client-based variables.

Abstain from eating and drinking within 4 hours of the test
Avoid exercising within 12 hours of the test
Void (urinate) completely prior to testing
Do not drink alcohol within 48 hours of the test
Avoid taking diuretics prior to testing unless instructed by your doctor

Advantages

Requires little or no technical knowledge of the operator or the client
Testing itself takes less than a minute
The unit can be easily transported from place to place
Requires only an electrical outlet and the machine itself

Disadvantages

This method has a higher standard error range than most people desire
Tends to consistently overestimate lean people and underestimate obese people
The accuracy BIA does have is very dependant on multiple variables which may be hard to control for some people

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